To confer fluidity, admixtures (high-performance water reducing admixtures) such as those based on naphthalene, melamine, aminosulfonic acid or polycarboxylic acid have been used in hydraulic compositions such as concrete. Admixtures such as water-reducing admixtures are desired to have various capabilities such as conferment of fluidity on hydraulic compositions, retainability of fluidity (fluidity retention), and prevention of delay in hardening. From this viewpoint, there are also proposed improvements in the polycarboxylic acid-based admixtures.
For example, JP-A 7-247149 discloses that polymers obtained by polymerizing carboxylate monomers having a specific structure are used as an agent for preventing decrease in concrete fluidity and used in combination with a known cement admixture.
JP-A 10-81549, which corresponds to U.S. Pat. No. 5,911,820 or EP-B 846090, discloses that a concrete admixture composed of copolymers having specific ethylenically unsaturated monomer units and ethylenically unsaturated carboxylate units as structural units is used in combination with a high-performance water reducing admixture.